title: Environmental dust exposure as a factor contributing to an increase in Escherichia coli O157 and Salmonella populations on cattle hides in feedyards.
abstract: A study was conducted to determine the impact of exposure to dust in the cattle load-out area in feedyards on pathogen contamination of cattle hides. A total of 250 cattle hides were sampled during summer and fall months, which are associated with elevated prevalence of Escherichia coli O157 in West Texas. Animals were removed from their home pens and restrained in a chute and sampled prior to exposure to dust generated as a result of a simulated loading exercise. The cattle hides were sampled again after exposure to the loading dust to determine total numbers of pathogens on cattle hides on leaving their home pen (before loading) and on cattle hides after exposure to the dust in the loading area. Air and dirt samples from the home pens and the cattle load-out area were also collected. The presence of E. coli O157 and Salmonella was determined in all the samples, and when a positive sample was identified, the total numbers of these bacteria present were enumerated. The total numbers of pathogens increased after dust exposure; Salmonella counts increased from 1.09 log most probable number (MPN)/cm2 to 1.74 log MPN/cm2 after exposure, and E. coli O157 counts increased from 0.80 to 2.35 log MPN/cm2 after sampling. E. coli O157 and Salmonella were recovered from the air samples during dust generation at 6.66 and 11.1%, respectively. Salmonella and E. coli O157 prevalence was not changed and was not associated with the exposure to the dust. Results indicate airborne dust generated as a result of cattle movement and loading could be an important determining factor in total numbers of pathogens recovered on cattle hides.
authors.affiliation: Department of Animal and Food Sciences, International Center for Food Industry Excellence, Texas Tech University, P.O. Box 42141, Lubbock, Texas 79409, USA.
authors.forename: M F
authors.initials: MF
authors.lastname: Miller
authors.forename: G H
authors.initials: GH
authors.lastname: Loneragan
authors.forename: D D
authors.initials: DD
authors.lastname: Harris
authors.forename: K D
authors.initials: KD
authors.lastname: Adams
authors.forename: J C
authors.initials: JC
authors.lastname: Brooks
authors.forename: M M
authors.initials: MM
authors.lastname: Brashears
mesh_terms: D000391:Air Microbiology; D000822:Animal Husbandry / Q000379:methods; D000818:Animals; D002417:Cattle / Q000382:microbiology*; D015169:Colony Count, Microbial; D004391:Dust; D004783:Environmental Microbiology; D019453:Escherichia coli O157 / Q000254:growth & development / Q000302:isolation & purification*; D005506:Food Contamination / Q000032:analysis / Q000517:prevention & control; D005516:Food Microbiology; D006801:Humans; D012475:Salmonella / Q000254:growth & development / Q000302:isolation & purification*; D012867:Skin / Q000382:microbiology*; D014186:Transportation
chemical_list: D004391:Dust